The effect of pruning and girdling on root: Shoot interactions in sour orange seedlings

Abstract

Greenhouse grown sour orange (Citrus aurantium L.) seedlings were pruned back to 1/3 of the original height or 8 cm tall. One treatment removed 70% (+L) and the other 100% (‐L) of the original foliage. In addition, stem was girdled to remove bark strips encircling 1/3, 2/3, or 3/3 of the stem circumference. At 0–2/3 girdling, the ‐L pruning treatment resulted in less new shoot growth and dry matter production and increased leaf levels of N, K, Mg, Ca, Zn, and Cu compared to the +L pruning treatment. Increases in leaf N, K, Mg, and Ca at ‐L pruning treatment were accompanied by lower levels of those elements in roots and/or stems indicating that retranslocation within the plant could have been responsible for elevated leaf N, K, Mg, and Ca levels. Increased absorption in relation to dry matter production was responsible for higher leaf Zn and Cu levels. Mineral nutrient uptake was reduced in plants completely girdled due to the shortage of energy in roots and possibly also a shortage of a shoot produced hormones. Partial girdling of the stem had a negligible effect on seedlings growth and nutrient status since the remaining bark at the site of girdling increased in thickness and probably compensated for that removed.

Key words:

• Citrus aurantium L
• mineral nutrients
• root: shoot ratio